Removal of small nonenveloped viruses by antibody‐enhanced nanofiltration during the manufacture of plasma derivatives

Abstract

Filters with nominal pore sizes in the nanometer range are well-established tools for enhancing the virus safety margins of plasma-derived products, yet intrinsically less successful for smaller viruses such as hepatitis A virus (HAV) and human parvovirus B19 (B19V). The formation of virus-antibody complexes increases the effective size of these smaller viruses and would thus improve their removal by nanofiltration. While the principle of virus removal by antibody-dependent nanofiltration has been demonstrated with animal antisera and viruses spiked into human plasma product intermediates, the significance of these results remains unclear due to the potential contributions of xenoanti-bodies and/or heteroagglutination in such heterologous systems. The current study investigated antibody-dependent virus removal by nanofiltration in a heterologous animal parvovirus system to establish the concentration dependence of the effect. In addition, the phenomenon was investigated in a homologous system with custom-made HAV and B19V antibody-free and -containing human immunoglobulin intermediates. Viruses were analyzed with infectivity assays and fully validated polymerase chain reaction assays that also circumvent the obscuring effects of neutralizing antibodies with infectivity assays. By use of the heterologous mice minute virus and the homologous HAV and B19V systems, viruses passed the 35-nm (Planova 35N) filter in the absence of specific antibodies. Beyond a threshold virus antibody concentration, nanofiltration resulted in effective virus removal of viruses smaller than the nominal pore size of the filter used. HAV and B19V are effectively removed by antibody-dependent 35N nanofiltration, already at intermediate antibody concentrations well below those comparable to human plasma pools for fractionation.